FIG. 1 is a schematic diagram illustrating a frame structure in a time division duplex (TDD) mode in an LTE system. The frame structure is also referred to as frame structure type 2. In the frame structure, one 10 ms (which occupies 307200 Ts, with 30720 Ts/ms) radio frame is divided into two half-frames, the length of each half-frame is 5 ms (i.e. 153600 Ts), each half-frame contains 5 subframes, and the length of each subframe is 1 ms. The function of each subframe is shown in Table 1. Specifically, D denotes a downlink subframe for transmitting a downlink signal, and U denotes an uplink subframe (also referred to as a normal uplink subframe) for transmitting an uplink signal. In addition, one uplink/downlink subframe is divided into 2 time slots, and the length of each time slot is 0.5 ms. S denotes a special subframe, which contains three special time slots, i.e. a downlink pilot time slot (DwPTS), a guard period (GP) and an uplink pilot time slot (UpPTS). In an actual system, an uplink/downlink configuration index may be notified to a user equipment (UE) through a broadcasting message.
TABLE 1SwitchpointSubframe numberConfigurationperiodicity012345678905 msDSUUUDSUUU15 msDSUUDDSUUD25 msDSUDDDSUDD310 ms DSUUUDDDDD410 ms DSUUDDDDDD510 ms DSUDDDDDDD
A frame structure in a frequency division duplex (FDD) mode in the LTE system is also referred to as frame structure type 1, as shown in FIG. 2. One 10 ms radio frame is divided into 20 time slots, and the length of each time slot is 0.5 ms. 2 adjacent time slots constitutes a subframe of a length of 1 ms, i.e. subframe i is composed of time slot 2i and time slot 2i+1, where i=0, 1, 2, . . . 9. In the FDD mode, 10 subframes are all used for transmitting the uplink or downlink signals, and the uplink and downlink signals are differentiated from each other by different frequency bands.
In the LTE system, resource allocation is performed by taking a physical resource block (PRB, which is briefly referred to as a resource block (RB)) as a unit. One PRB occupies 12 subcarriers (a subcarrier also referred to as a resource element (RE), and the frequency of each subcarrier is 15 kHz) in a frequency domain, and occupies one time slot in a time domain, i.e. occupies 7 SC-FDMA symbols of normal cyclic prefix (Normal CP) or 6 SC-FDMA symbols of extended cyclic prefix (Extended CP) in the time domain. If an uplink system bandwidth corresponds to NRBUL RBs in total in the frequency domain, the indexes of the RBs are 0, 1, . . . , NRBUL−1, and the indexes of the REs are 0, 1, . . . , NRBUL·NSCRB−1, where NSCRB is the number of the subcarriers that an RB corresponds to in the frequency domain. Taking the Normal CP for example, the structure of the PRB is shown in FIG. 3.
A scheduling request (SR) is a request signal sent from a UE to a base station when the UE hopes to send signals at a higher data rate. It is specified that the SR signal is transmitted over a physical uplink control channel (PUCCH). The UE acquires a corresponding SR periodicity and subframe offset according to an SR configuration index ISR sent from the base station, as shown in Table 2.
TABLE 2SR configurationSR periodicitySRindex ISR(ms)subframe offset0-4 5ISR 5-1410ISR − 515-3420ISR − 1535-7440ISR − 35 75-15480ISR − 75155OFFN/A
For example, if the SR configuration index ISR sent from the base station is 6, the UE can find that the SR periodicity is 10 ms and the SR subframe offset is ISR−5=6−5=1 from Table 2.
According to the above-mentioned table, it is only determined how the UE can obtain a sending periodicity for the SR signal and the subframe offset thereof according to ISR, but it is not indicated in which subframe of radio frame the UE sends the SR signal. This means that the UE cannot be ensured to utilize the radio frame sufficiently and effectively, and this even causes that the SR signal sent from the UE may not be received reliably by the base station. Therefore, it is currently required to propose a method which can allow the UE to determine the radio frame and subframe for sending the SR signal according to the SR sending periodicity and the subframe offset.